Separation of hydrocarbon mixtures into constituent parts



Patented Dec. 31, 1935 UNITED STATES PATENT OFFICE SEPARATION OF HYDROCARBON MIX- TURES INTO CONSTITUENT PARTS James M. Whiteley, Roselle, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Original application December 21,

1931, Serial N0 582,501. Divided and this application August 3, 1933, Serial No. 683,510

30laims.

This invention relates to the separation of hydrocarbon mixtures into constituent parts; and more specifically comprises a method for separating such hydrocarbon mixtures into fractions of difierent molecular weight and/or fractions of dissimilar hydrocarbon structure by means of a' selective hydrocarbon solvent.

The term hydrocarbon mixtures is intended to include hydrocarbon oils such as heavy gas oils, lubricating distillates, cylinder oils, residual oils, fuel oils and the like, as well as waxy hydrocarbon materials, such as petrolatum and paraffln wax or mixtures of oil and wax, whether obtained' from petroleum, or bythe cracking, de-

structive distillation or hydrogenation of'shales,

coals, lignites, tars, pitches, bitumens and other .carbonaceous materials.

Hydrocarbon mixtures may be readily separated into fractions of different boiling point and molecular weight by distillation, fractionation or rectification- They may also be separated into fractions of dissimilar hydrocarbon structure.

that is, separated into paraflinic and aromatic or naphthenic fractions by means of selective solvents such as phenol, aniline, liquid sulfur.

dioxide, nitrobenzene and -the like. .In many cases, however, the application of heat even under high vacuum to. heavy oils in order to distill the lower boiling fractions may be undesirable" due to the cracking and polymerization which occurs. The use of the common selective solvents is wasteful and expensive and necessitates subsequent complete elimination of the solvent which is always a non-hydrocarbon-material.

I have now found that hydrocarbon mixtures may be separated into their constituent parts according to molecular weight and/or hydrocarbon structure by the incorporation therewith of a selective hydrocarbon solvent. This avoids the necessity for applying heat and has the additiona1 great advantage that .the agent of separation is a hydrocarbon itself. The method by which this separation may be effected and the nature of the preferred selective hydrocarbon solvents will be fully understood from the following description.

It has been indicated that separation may be made either according to molecular weight 'or according to hydrocarbon structure. If a mixture of wide boiling range is selected as theinitial material, separation will be principally ac-, cording to molecular weight and only a small amount of. separation according to structure occurs. If separation according to structure is principally desired it is preferable to startwith a mixture of more limited boiling range, say one with a boiling range of not more than 20 to 50 Il The hydrocarbon mixture to be separated into constituent parts is placed in a suitable vessel which is adapted to be maintained under a pressure suiiicient at the temperature employed to retain the light hydrocarbons used to. effect the separation in liquid phase.- Temperatures between say -40 and F., or even 200 F. are suitable, and pressures varyingfrom slightly above 10 atmospheric to- 50 or more atmospheres may be used.

- The hydrocarbon mixture is then .diluted with from 3 to 15 volumes or more of a selective hydrocarbon solvent, such as, for example. a liquefied normally gaseous hydrocarbon or mixture of liquefled hydrocarbons. 'If a hydrocarbon oil containing substantial amounts of asphaltic materials is to be treated, it is preferable to add the liquefied hydrocarbon tothe oil slowly or stepwise in small quantities, this to avoid a sudden precipitation of such asphalticmaterials and the entrapment of globules 01011 which results therefrom. Vigorous agitation may be provided to facilitate the mixing of the. hydrocarbon mixture 'with the diluent.

Selective hydrocarbon solvents suitable for the purpose of the present process comprise generally all those hydrocarbons the boiling point of which lies below about 0 C. Among these are methane. ethane, propane, butane, iso-butane, ethylene. propylene, butylene, iso-butylene or any mixture of these. Other hydrocarbons such as acetylene and cyclobutanemay also be used. Small quan- 35 tities of higher boiling hydrocarbons such as pentane, hexane. and even higher are not'*objectionable, but in general the lower boiling ydrocarbons are preferred. .The particular hydrocarbon or mixture of hydrocarbons chosen as the agent of separation will depend very largely on -der moderate pressures say about .15 atmosphones. more or less. depending upon the proportion of ethane to propane. The whole or a part of the normally gaseous hydrocarbon may if preferable be pumped into the hydrocarbon mixture in gaseous form and the whole mass then subjected to pressure to efiect the liquefaction.

The gases obtained in the cracking of hydrocarbons normally contain small quantities of these lighter hydrocarbons and such gases may,

be liquefied and used as the diluent. Gases obtained in the stabilization of gasoline furnish an especially suitable source of the preferred hydrocarbons, ethane and propane.

The quantity of liquefied hydrocarbon used naturally depends upon the nature of the material to be separated into constituent parts. If the mixture is a hydrocarbon oil sumcient diluent should be added to cause the formation of two distinct layers. If the mixture is a solid or waxy hydrocarbon the quantity of diluent should at least be sufiicient to dissolve the soluble portions of the mass.

Following dilution of the hydrocarbon mixture, the two layers or the two fractions into which the mixture has been divided are separated the one from the other by any suitable means, such as decanting, filtering or otherwise and the liquefied hydrocarbon diluent removed from each part by vaporization or other means. The recovered diluent may be recycled with a fresh p rtion of material as will be understood. Prior clay or charcoal. Filtration in the light hydrocarbon solution is extremely rapid and efficient andresults in an improved color and appearance of the separated products.

Although the above described method of separating hydrocarbon mixtures into constituent parts is applicable to all types of hydrocarbons whether liquid, solid, or combinations. of liquid and solid, it is particularly adapted to the separation of heavy hydrocarbon oils, especially the .lubricating fractions of petroleum 0115, into component oils of dissimilar composition'and characteristics. 4

When working with petroleum oils 9. mixture of propane and ethane. provides a very satisfactory selective solvent or separation agent. If such a solvent ismsed the ethane should be present in an amount preferably above say and below say 85%, although similar or larger quantities may be used. By increasing the proportion'of ethane in the selective solvent the volume of heavy oil thrown out in'the bottom layer is correspondingly increased. Depending therefore upon what degree of separation is desired the ratio of ethane to propane may be increased or decreased. This of course applies also to other mixtures of hydrocarbons of 2 carbon atoms or less with hydrocarbons of 3 carbon atoms or more. When only 15% ethane is used the bottom layer contains a very small amount of a high molecular weight and high viscosity 011. On the other hand when 85% ethane is used the bottom layer comprises a very large proportion of the oil and has a correspondingly lower viscosity.

' 87% of the original oil and the bottomlayer only and naphthenic hydrocarbons .such as liquid sulfur dioxide, phenol, aniline, nitrobenzene and the like, in addition to the liquefied hydrocarbons which latter exhibit a selective solvent action for the parafilnic hydrocarbons.

By controlling the proportion of ethane and propane used, the total volume of diluent, and

p the temperature and pressure atwhich the process is carried out it is possible to separate heavy hydrocarbon oils into fractions of diiferent viscos- 10 pheres. Two distinct layers are formed which are separated and the liquefied hydrocarbon removed by vaporization. The top layer is found to contain 38% of the original oil, the bottom layer 62%. A comparison of the characteristics of the original oil and the top and bottom layers 5 follows:

. si l Bottom on Top layer by Gravity A. 2.1 22.9 26.5 I 20.8 Saybolt viscosity at 100 F--. 8016 B46 6886 Saybolt viscosity at 210 F--- 146 80 231 Carbon 2. 479 0. 488 8. 67 Viscosity indel. 77 96 75 The viscosity index, V. 1., indicates the relation between the viscosity at 100 F. and the viscosity at 210 F. and is such that the smaller the difference in viscosity at these'two temperatures the higher is the V. I. It is defined by Dean and 40 Davis in Chemical and Metallurgical Engineering, vol. to, No. 10, October 1929.

To illustrate the eifect of varying the proportion of ethane and propane used another portion of the mass oil is diluted with 5 volumes of propane and only 3' volumes of ethane. .When the two layers are separated and the propane and ethane are flashed off, the top layer is found to contain This example shows that bydecreasing the proportion ofethane used the volume of -oil thrown out is reduced. The increase in V. I. of the oil 1 in the top layer over the V. I. of the original 011,

however, is correspondingly reduced. For ex- 56 ample, in this last example the V. I. of the top layerwas only 80 as compared with 96 in the first example.

This invention is not limited by any theory of the mechanism of the separation nor by any de- 00 tails or examples which have been given merely for illustrative purposes, but is limited only by the following claims in which I wish to claim all novelty inherent in the invention.

A finished 15 This application is a division of my copending application, Ser."No. 582,501, filed December 21, 1931.

I claim:

1. In the art of refining mineral oil comprisin naphthenic and parafilnic constituents, the step comprising extracting the oil with phenol in the presence of an added liquid having greater solvent power forparafiinic constituents of the 01! than for naphthenic constituents thereof.

2. In the art of refining nfineral oil comprisin naphthenic and paraflinic constituents, the step comprising extracting the oil with phenol in the presence of an added hydrocarbon having a boiling range substantially below the boiling point of the oil, the said hydrocarbon being adapted to form a two layer system with the phenol and oil.

3. In the art of refining mineral oil comprising naphthenic and parafflnic constituents, the step comprising extracting the oil with phenol in the presence of an added liquefied normally gaseous hydrocarbon, the said added hydrocarbon being adapted to form a two layer system with the phenol and oil.

JAMES M. WHI'IEIEY. 

